Method for supplying cutting oil

ABSTRACT

A method for supplying cutting oil which is able to attain the above object by adopting the following processes in a machine tool for cutting work pieces.
         a. setting of individual cutting times to each work piece and selection of cutting oil to be used,   b. setting of a quantity of the cutting oil supplied per unit time to a cutting area where the cutting oil selected by the process a is used,   c. supplying the cutting oil to a cutting-oil tank, with a state kept that the cutting oil remains in the cutting-oil tank, and   d. supplying the cutting oil to the cutting area on cutting each of the work pieces by setting a quantity of the cutting oil as a quantity obtained by multiplying individual cutting times according to the process a with a cutting quantity per individual unit times according to the process b.

TECHNICAL FIELD

The present invention relates to a method for supplying cutting oilwhich is used in a machine tool for cutting work pieces to a cutting-oiltank and a cutting area.

BACKGROUND ART

Where a machine tool is used to cut work pieces, it is essential tosupply cutting oil to a cutting area in order to cool heat generated atthe cutting area and also reduce cutting resistance.

It is well known that a quantity of cutting oil to be supplied iscontrolled corresponding to cutting of a work piece.

For example, in Patent Document 1, cutting oil to be supplied to acutting area is varied in quantity, depending on a change in cuttinglength and cutting resistance (claims 1, 2 and 3), and in PatentDocument 2, cutting oil to be supplied to a cutting area is controlledfor a quantity thereof corresponding to loads of a driving motornecessary for cutting (Abstract).

A machine tool is provided with a cutting-oil tank for supplying cuttingoil to a cutting area. Each of the above-described prior arts requiressuch a technical premise that cutting oil is normally supplied to acutting-oil tank as a matter of course.

However, the above-described technical premise is not always satisfied.

Explaining concretely, quantity of cutting oil supplied per unit time toa cutting area is different according to each workpiece. However in theprior arts, where one or a plurality of types of work pieces are cut, aspecial technical consideration is not necessarily given to appropriatesupply of cutting oil to a cutting-oil tank so that the cutting oil canbe supplied appropriately from the cutting-oil tank on cutting each workpiece.

Incidentally, Patent Document 3 discloses a configuration in whichcutting oil separated from chips is supplied to a cutting-oil tank 3(Abstract). However, in this case, no adjustment is set for a quantityof the cutting oil to be supplied to the cutting-oil tank afterconsideration is given to a quantity of the cutting oil necessary forcutting a work piece.

Patent Document 4 discloses a configuration in which a first cutting-oiltank and a second cutting-oil tank are adjusted so as to besubstantially equal in temperature (claim 1). However, no adjustment isset for a quantity of cutting oil supplied to both the cutting-oil tanksafter consideration is given to a quantity of the cutting oil necessaryfor cutting a work piece.

When cutting oil is not supplied sufficiently to the cutting-oil tanks,resulting in outflow from the tanks and the cutting oil is supplied to acutting area in a larger quantity than before, cutting work must bestopped because the cutting oil is used up in the cutting-oil tanks.

The above-described stopping inevitably causes a serious decrease inwork efficiency of a machine tool.

In order to avoid the above-described state of stopping, there can beexpected such a method that when cutting oil inside a cutting-oil tankreaches a minimum reference quantity, the cutting oil is automaticallysupplied from a cutting-oil supply source to the cutting-oil tank toachieve a state in excess of the minimum reference quantity.

Cutting oil necessary for cutting work pieces is different in quantity,according to the types of work pieces. However in the above-describedmethod, a reference quantity by which the cutting oil is supplied to thecutting-oil tank is not necessarily clear, with the above differencetaken into account.

As is above described, in prior arts, it may be estimated that notechnically significant proposal has been set about supply of cuttingoil to a cutting-oil tank or a cutting area in an appropriate quantityafter consideration is given to the fact that the cutting oil isdifferent in a necessary quantity according to the types of work piecesto be cut.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] Japanese Published Unexamined Patent Application    No. H6-023651-   [Patent Document 2] Japanese Published Unexamined Patent Application    No. H6-23612-   [Patent Document 3] Japanese Published Unexamined Patent Application    No. H8-196826-   [Patent Document 4] Japanese Patent No. 5202142

SUMMARY OF INVENTION Problem to be Solved

An object of the present invention is to provide a configuration whichsupplies cutting oil appropriately to a cutting-oil tank and a cuttingarea based on the fact that in a machine tool for cutting work pieces,the cutting oil is different in a necessary quantity according to typesof the work pieces.

Means for Solving the Problem

In order to solve the above problem, a basic configuration of thepresent invention stands on following of (1), (2), (3), (4), (5) and(6).

(1) The following processes have been adopted in a method for supplyingcutting oil to a machine tool for cutting work pieces:

a: setting cutting times t₁, . . . , t_(i), . . . , t_(n) for workpieces 1, . . . , i, . . . , n and selection of cutting oil to be usedwherein n is an integer of one or more,

b: setting quantities q₁, . . . , q_(i), . . . , q_(n) of the cuttingoil supplied per unit time according to a cutting area of the workpieces 1, . . . , i, . . . , n, where the cutting oil selected byprocess a is used,

c: supplying the cutting oil to a cutting-oil tank, with such a statekept that the cutting oil remains in the cutting-oil tank, and

d: supplying the cutting oil to the cutting area by setting quantitiesof the cutting oil to be q₁t_(i), . . . , q_(i)t_(i), . . . , q_(n)t_(n)on cutting the work pieces 1, . . . , i, . . . , n.

(2) The method for supplying cutting oil according to theabove-described (1), wherein

when a volume of the cutting-oil tank is given as V in the method forsupplying the cutting oil to the cutting-oil tank that is described inprocess c, a quantity q of a fixed value supplied per unit time is setunder the condition that

inequalities of q>q₁, . . . , q_(i), . . . , q_(n) andq≤(V+q ₁ t ₁ + . . . +q _(i) t _(i) + . . . +q _(n) t _(n))/(t ₁ + . . .+t _(i) + . . . +t _(n))  [Formula 1]are each satisfied, and the cutting oil is continuously supplied to thecutting-oil tank by the quantity q over an entire period of time duringwhich the work pieces 1, . . . , i, . . . , n are cut.

(3) The method for supplying cutting oil according to theabove-described (1), wherein

a quantity q′ is set as a fixed value to be supplied to the cutting-oiltank per unit time, wherein for some i₀<n:q′≤(V+q ₁ t ₁ + . . . +q _(i0) t _(i0))/(t ₁ + . . . +t _(i0)) andq′>(q ₁ t ₁ + . . . +q _(n) t _(n))/(t ₁ + . . . +t _(i0))wherein V is the volume of the cutting-oil tank, and the quantity of theoil in the cutting-oil tank before cutting is set to be zero, and

supplying the cutting oil to the cutting-oil tank by the quantity q′over a period of time t_(l)+ . . . +t_(i0), and thereafter not supplyingthe cutting oil to the cutting-oil tank.

(4) The method for supplying cutting oil according to theabove-described (1), wherein

when a volume of the cutting-oil tank is given as V in the method forsupplying the cutting oil to the cutting-oil tank that is described inprocess c, setting each quantity q₁″, . . . , q_(i)″, . . . , q_(n)″ ofa fixed value supplied per unit time under condition that

inequalities ofq _(i) ″>q ₁ , . . . ,q _(i) , . . . ,q _(n) and(q ₁ ″−q ₁)t ₁+ . . . +(q _(i) ″−q _(i))t _(i)+ . . . +(q _(n) ″−q_(n))t _(n) ≤V,are each satisfied, and the cutting oil is supplied to the cutting-oiltank at each of the quantities q₁″, . . . , q_(i)″, . . . , q_(n)″,corresponding to cutting each of the work pieces 1, . . . , i, . . . ,n.

(5) The method for supplying cutting oil according to theabove-described (1), wherein

in the method for supplying the cutting oil to the cutting-oil tank thatis described in process c, setting a quantity q″″ of a fixed valuesupplied per unit time under conditions that

selecting a maximum value q_(m) among q₁, . . . , q_(i), . . . , q_(n),an inequality of q″′>q_(m) is satisfied,

and the cutting oil is supplied to the cutting-oil tank by the quantityq″′ continuously corresponding to cutting the work pieces 1, . . . , i,. . . , n, then supply of the cutting oil to the tank is stopped in astage that the cutting-oil tank is filled with the cutting oil, and thecutting oil is again supplied to the cutting-oil tank by the quantityq″′ at a stage that the quantity of the cutting oil retained in thecutting-oil tank has reached a minimum reference quantity due to thethus stopped supply, and thereafter the stopping and the supply arerepeated according to necessary case.

(6) The method for supplying cutting oil according to theabove-described (1), wherein

in the method for supplying the cutting oil to the cutting-oil tank thatis described in process c, cutting oil Q₀ of an initial referencequantity is supplied in advance to the cutting-oil tank prior to cuttingof the work pieces 1, . . . , i, . . . , n, and after start of cuttingof the work pieces 1, . . . , i, . . . , n, the cutting oil is suppliedto the cutting-oil tank by the individual quantities q₁, . . . , q_(i),. . . , q_(n) of the cutting oil per unit time corresponding to thecutting times t₁, . . . , t_(i), . . . , t_(n).

Advantageous Effects of Invention

In the present invention standing on the basic configurations of (1),(2), (3), (4), (5) and (6), it is possible to continue cutting the workpieces without stopping, corresponding to individual types of the workpieces to be cut, by supplying the cutting oil to a cutting area so asto prevent the cutting oil from being used up in a cutting-oil tank andkeeping such a state that the cutting oil remains therein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart which shows steps of the basic configuration (1).

FIG. 2 is a flowchart which shows steps of the basic configuration (2).

FIG. 3 is a flowchart which shows steps of the basic configuration (3).

FIG. 4 is a flowchart which shows steps of the basic configuration (4).

FIG. 5 is a flowchart which shows steps of the basic configuration (5).

FIG. 6 is a flowchart which shows steps of the basic configuration (6).

DESCRIPTION OF EMBODIMENTS

The basic configuration (1) shows a basic principle of the presentinvention.

Specifically, in the process a, each of the cutting times t₁, . . . ,t_(i), . . . , t_(n) is set for each of the work pieces to be cut, 1, .. . , i, . . . , n and cutting oil to be used is selected, therebysetting and selecting basic technical matters of all the processeswherein n is an integer of one or more.

In the process b, when the work pieces 1, . . . , i, . . . , n are cut,the quantities q₁, . . . , q_(i), . . . , q_(n) of the cutting oilsupplied per unit time are set according to a cutting area. Thesequantities supplied per unit time are based on an understanding of anappropriate maximum value and an appropriate minimum value obtained frompast experiences or experiments performed in advance, theabove-described quantities q₁, . . . , q_(i), . . . , q_(n) aretherefore to be selected within a range of the maximum value and theminimum value.

In the process c, the cutting oil in the quantities q₁t₁, . . . ,q_(i)t_(i), . . . , q_(n)t_(n) to flows out from the cutting-oil tankand also is supplied to the cutting area in a cutting step of the workpieces 1, . . . , i, . . . , n selected and set by the processes a andb. The cutting oil is supplied in a quantity in excess of the quantitywhich has flowed out from the cutting-oil tank, that is, with a state ofretaining the cutting oil.

Therefore, when a quantity of the cutting oil supplied to thecutting-oil tank until cutting of the work pieces 1, . . . , i is givenas Q, it is essential that an inequality of Q−(q₁t₁+ . . .+q_(i)t_(i))>0 is satisfied in a range of i=1˜n.

Such an embodiment that the above-described inequality is automaticallysatisfied will be as per described later in accordance with the basicconfigurations (2) to (6). In the process c, the above-describedinequality is not only satisfied automatically but also satisfied byartificial processing with a manual operation.

Explaining according to concrete example, in a cutting stage of the workpieces 1, . . . , i, a quantity supplied per unit time is manually setso that a quantity Q₁ of cutting oil in excess of quantities of q₁t₁+ .. . +q_(i)t_(i) can be supplied to the cutting-oil tank during a periodof time t₁+ . . . +t_(i), and in a cutting stage of the work pieces i+1,. . . , n, a quantity supplied per unit time is set manually so that aquantity Q₂ of the cutting oil in excess of q_(i+1)t_(i+1)+ . . .+q_(n)t_(n) can be supplied f rom a supply source to the cutting-oiltank during a period of time t_(i+1)+ . . . +t_(n), thus making itpossible to perform such processing that can satisfy the above-describedinequality.

The above-described processing can be achieved, as a matter of course,not only the example divided by two stages as described above but alsoan example divided by a single stage or by three or more stages.

In the process of d, under a premise that the cutting oil is supplied tothe cutting-oil tank according to the process c and on the basis ofcutting times t₁, . . . , t₁, . . . , t_(a) set by the process a and thequantities q₁, . . . , q_(i) of the cutting oil supplied per unit timeset by the process b, corresponding to cutting of the work pieces 1, . .. , i, . . . , n, the cutting oil flows out from the cutting-oil tank inquantities q₁t₁, . . . , q_(i)t_(i), . . . , q_(n)t_(n) and also issupplied to the cutting area, and so a step of the final stage isachieved.

Then, at a stage that cutting of the work pieces 1, . . . , i is ended,the cutting oil is supplied to the cutting area in quantities of (q₁t₁+. . . +q_(i)t_(i)).

Now the cutting oil is subjected to circulation processing in which,after supply to a cutting area, the cutting oil is ordinarily returnedagain to the cutting-oil tank by removing chips, etc., generated by thecutting by an evaporation occurring from the above-described circulationand also by the removal with disposal of waste including chips, etc.,the cutting oil is gradually decreased in quantity. So the cutting oilis supplied to the cutting-oil tank by replacement of the thus decreasedquantity.

Each of the processes of a to d in the basic configuration (1) can besummarized by the flowchart of FIG. 1 .

The basic configurations (2) to (5) correspond to an embodiment whichautomatically achieves the process of c in the basic configuration (1).

In the basic configuration (2), the cutting oil is supplied in a fixedquantity of q per unit time over an entire period of time during whicheach of the work pieces 1, . . . , i, . . . , n is cut.

In the basic configuration (2), since selected q satisfies an equationof q>q₁, . . . , q_(i), . . . , q_(n),q(t ₁ + . . . +t _(i))−(q ₁ t ₁ + . . . +q _(i) t _(i))=(q−q ₁)t ₁+ . .. +(q−q _(i))t _(i)>0  [Formula 2]is satisfied, and the above-described inequality is satisfied until i=n,thus it is possible to retain a state that the cutting oil is not usedup in the cutting-oil tank but remains in the cutting-oil tank.

In the basic configuration (2), since the above-described inequality issatisfied, the cutting oil retained in the cutting-oil tank is increasedin quantity according to sequential cutting of the work pieces 1, . . ., i, . . . , n.

In the basic configuration (2), when a volume of the cutting-oil tank isgiven as V, since the followingq≤(V+q ₁ t ₁ + . . . +q _(i) t _(i) + . . . +q _(n) t _(n))/(t ₁ + . . .t _(i) + . . . +t _(n))  [Formula 3]is satisfied, therefore the followingq(t ₁ + . . . +t _(i) + . . . +t _(n))−(g ₁ t ₁ + . . . +q _(i) t _(i) +. . . +q _(n) t _(n))≤V  [Formula 4]is satisfied. A difference between a quantity of the cutting oilsupplied to the cutting-oil tank and a quantity flowed out from thecutting-oil tank is not more than a volume V of the cutting-oil tank.Thus, the cutting-oil tank may be filled up with the cutting oil but thecutting oil will not overflow.

If consideration is given to the inequality of q, that is, q>q₁, . . . ,q_(i), . . . , q_(n) and the inequality of [Formula 3], it is essentialthat the inequality ofq _(i)(t ₁ + . . . +t _(i) + . . . +t _(n))<(V+q ₁ t ₁ + . . . +q _(i) t_(i) + . . . +q _(n) t _(n))  [Formula 5]is satisfied on cutting the work pieces 1, . . . , i, . . . , n, and thebasic configuration (2) entirely stands on satisfaction of theabove-described inequalities.

The basic configuration (2) is characterized by the cutting-oil beingconstantly supplied to the cutting-oil tank in a steady state, andprocess corresponding to processes c and d of the basic configuration(1) can be summarized by a flowchart of FIG. 2 .

In the basic configuration (3), when a volume of the cutting-oil tank isgiven as V in the process of c, after selection of i=i₀ in which(V+q ₁ t ₁ + . . . +q _(i) t _(i))/(t ₁ + . . . +t _(i))  [Formula 6]is given as a minimum value, the cutting oil is supplied to thecutting-oil tank intermittently, that is, the cutting oil is supplieduntil cutting of a work piece i₀ but no cutting oil is suppliedthereafter under conditions of i₀≤n−1.

In the basic configuration (3), there is set a quantity q′ of thecutting oil supplied per unit time to the cutting-oil tank which willsatisfyq′≤(V+q ₁ t ₁ + . . . +q _(i0) t _(i0))/(t ₁ + . . . +t _(i0))  [Formula7]andq′>(q ₁ t ₁ + . . . +q _(n) t _(n))/(t ₁ + . . . +t _(i0)).  [Formula 8]

In the case of i=i₀, if consideration is given to the fact that theabove-described [Formula 6] is minimum,q′≤(V+q ₁ t ₁ + . . . +q _(i0) t _(i0))/(t ₁ + . . . +t _(i0))≤(V+q ₁ t₁ + . . . +q _(i) t _(i))/(t ₁ + . . . +t _(i))(i=1, . . . ,n−1)is satisfied in relation to the above-described [Formula 6] which is notlimited to i=i₀.

Therefore, in a range of i=1, . . . , i, . . . , n−1,q′(t ₁ + . . . +t _(i))−(q ₁ t ₁ + . . . +q _(i) t _(i))≤Vis satisfied, and then in a cutting stage of the work pieces 1, . . . ,i, . . . , n−1, the cutting oil will never overflow from the cutting-oiltank.

Further, in a cutting stage of a work piece of n, as long as no cuttingoil is supplied to the cutting-oil tank in a quantity of q′ supplied perunit time, as a matter of course, the cutting oil will not overflow fromthe cutting-oil tank in any of the cutting steps.

Since, by the inequality of [Formula 8],q′(t ₁ + . . . +t _(i0))−(q ₁ t ₁ + . . . +q _(i) t _(i) + . . . +q _(n)t _(n))>0is satisfied, it is possible to keep a state that the cutting oilremains in the cutting-oil tank without being used up in the cutting-oiltank.

When consideration is set to the inequalities of [Formula 7] and[Formula 8] on q′, in the basic configuration (3), there is a basicpremise thatq ₁ t ₁ + . . . +q _(i) t _(i) + . . . +q _(n) t _(n) <V+q ₁ t ₁ + . . .+q _(i0) t _(i0)is satisfied, in other words,q _(i0+1) t _(i0+1) + . . . +q _(n) t _(n) <Vis satisfied.

The basic configuration (3) is characterized by finishing supply of thecutting oil to the cutting-oil tank in a short period of time when i₀giving [Formula 6] as a minimum value is apparently smaller than a totalnumber n of the work pieces and process corresponding to processes c andd of the basic configuration (1) can be summarized by a flowchart ofFIG. 3 .

In the basic configuration (4), the cutting oil is supplied in such astate that a quantity supplied to the cutting-oil tank per unit time canbe changed corresponding to a sequential change of a work piece i whichis to be cut.

In the basic configuration (4), each q_(i)″ which satisfies inequalitiesofq _(i) ″>q ₁ , . . . ,q _(i) , . . . ,q _(n)and(q ₁ ″−q ₁)t ₁+ . . . +(q _(i) ″−q _(i))t _(i)+ . . . +(q _(n) ″−q_(n))t _(n) ≤V  [Formula 9]is set, and the cutting oil is supplied to the cutting-oil tank in thequantity of q_(i)″ supplied per unit time corresponding to cutting ofeach work piece i.

By the above-described inequalities between q and q₁, . . . , q_(i),q ₁ ″t ₁ + . . . +q _(i) ″t _(i)−(q ₁ t ₁ + . . . +q _(i) t _(i))=(q ₁″−q ₁)t ₁+ . . . +(q _(i) ″−q _(i))t _(i)>0  [Formula 10]is satisfied, and there is reliably no possibility that the cutting oilin the cutting-oil tank becomes empty when a work piece i is being cutat any stage from the start of cutting to a halfway cutting thereof, andthis will be also kept unchanged even at the final stage of i=n.

The cutting oil in the cutting-oil tank is increased in quantity ascutting of the work pieces 1, . . . , i, . . . , n proceedssequentially.

However the above-described inequality of [Formula 9] shows that adifference between a quantity of the cutting oil supplied to thecutting-oil tank and a quantity flowed out from the cutting-oil tank isnot more than the volume V of the cutting-oil tank and also means thatno cutting oil will overflow from the cutting-oil tank.

The basic configuration (4) is characterized by supplying the cuttingoil appropriately corresponding to a change in the work pieces to becut, and processes corresponding to processes c and d of the basicconfiguration (1) can be summarized by a flowchart shown in FIG. 4 .

In the basic configuration (5), a maximum value q_(m) is selected amongquantities q₁, . . . , q_(i), . . . , q_(n) of the cutting oil suppliedper unit time, and the cutting oil is supplied to the cutting-oil tankin q″′>q_(m), in other words, in a quantity of q″′ supplied per unittime which is larger than the above-described maximum value q_(m).

Describing individual actions, when the cutting oil is supplied to thecutting-oil tank in the quantity of q per unit time, there is a casethat the cutting oil is supplied to the cutting-oil tank up to a fullcapacity thereof, that is, until the tank is filled up, however in thiscase, the supply is stopped.

Due to the above-described stopping, the cutting oil inside thecutting-oil tank is gradually decreased in quantity.

However, when the cutting oil is decreased to a minimum referencequantity, the cutting oil is again supplied to the cutting-oil tank in aquantity of q″ supplied per unit time, and operation of the stopping andthe supply is repeated according to necessary case.

A relationship between q and q_(m) can be set as a linear equation, forexample,q″′=αq _(m)+β (note that α>1,β≥0),and the relationship is not always limited thereto.

Now when a time lag between a state of a minimum reference quantitydetected by a controller and the supply of the cutting oil in thequantity of q″′ is expressed as Δt, it is essential that the minimumreference quantity is equal to or greater than q_(m)·Δt.

However, for safety, it is desirable that the minimum reference quantityis not set to be q_(m)·Δt as described above but set to be q_(m)·t_(m)after selection of the maximum time of t_(m) from t₁, . . . , t_(i), . .. , t_(n).

The basic configuration (5) is characterized by eliminating the need forcumbersome calculations by using the inequalities such as the basicconfigurations (2) to (4) and process corresponding to processes c and dof the basic configuration (1) can be summarized by a flowchart shown inFIG. 5 .

In the basic configuration (6), the cutting oil is supplied to thecutting-oil tank corresponding to the cutting times t₁, . . . , t_(i), .. . , t_(n) in quantities equal to the quantities q₁, . . . , q_(i), . .. , q_(n) of the cutting oil supplied per unit time for cutting the workpieces 1, . . . , i, . . . , n, and the cutting oil is, in advance,supplied in an initial reference quantity Q₀ before start of cutting.

When, on cutting the work piece 1, the cutting oil is supplied to thecutting-oil tank in a quantity of q_(i) that is a quantity supplied perunit time from the cutting-oil tank and the cutting oil is also suppliedfrom the cutting-oil tank to a cutting area in the quantity of q₁, theminimum reference quantity Q₀ will be theoretically sufficient as longas it is q₁·Δt or more on the assumption that a time lag between supplyof the cutting oil to the cutting-oil tank and the supply thereof to thecutting area is given as Δt.

However, in real action, it is desirable that the initial referencequantity is set to be Q₀=q₁·t₁, with consideration given to the safety.

The basic configuration (6) is simple in supplying the cutting oil inthat the cutting oil is supplied to the cutting-oil tank at the samepace as it is supplied to the cutting area.

That is, the basic configuration (6) does not need technical premisesset by the inequalities or requirements of the quantities as found inthe basic configurations (2), (3), (4) and (5).

The basic configuration (6) is characterized by the simple supply of thecutting oil as described above, and process corresponding to processes cand d of the basic configuration (1) can be summarized by a flowchartshown in FIG. 6 .

Hereinafter, a description will be given by referring to examples.

Example 1

Example 1 is characterized in that alarm signals are generated whenquantity of the cutting oil is decreased lower than a predeterminedquantity due to evaporation of the cutting oil from the cutting-oil tankor an accident such as leakage, etc., resulting from chips being cloggedin the cutting-oil tank, and in the case of leakage, the cutting oil issupplied to the cutting-oil tank in such a quantity per unit time that aquantity per unit time equal to a decreased quantity due to the leakageor a quantity larger than the above quantity per unit time is added to aquantity supplied before occurrence of the accident.

As long as the cutting oil is supplied to the cutting-oil tank and flowsout from the cutting-oil tank according to the basic configurations (1)to (6), there is no possibility that the cutting oil in the cutting-oiltank becomes empty.

It is, however, impossible to exclude any possibility of evaporation ofthe cutting oil or an accident due to leakage resulting from chips beingclogged in the cutting-oil tank.

So if the cutting oil is used up due to the evaporation or the leakageand no cutting oil remains, and as a result, there is no choice but tostop cutting work.

In Example 1, in the case of leakage, the cutting oil is supplied to thecutting-oil tank in such a quantity per unit time that is equal to adecreased quantity per unit time due to the leakage or a quantity largerthan the above quantity per unit time is added, by which it is possibleto continue cutting work without stopping also in a stage that theleakage from the cutting-oil tank has been recovered.

Example 2

Example 2 is characterized in that water-soluble cutting oil is adopted,by which the larger the content of water is, the higher theconcentration of the water-soluble cutting oil supplied to a cutting-oiltank is set.

The water-soluble cutting oil develops a compatible state of oilcomponents and water by an action of a surfactant.

When the concentration is different from a reference value, there is atendency that lubrication functions are decreased at a cutting portion.Thus, in Example 2, the larger the content of water in relation to thecutting oil inside the cutting-oil tank is, the higher the concentrationof the water-soluble cutting oil supplied to the cutting-oil tank isset, and then a ratio of cutting oil to the water inside the cutting-oiltank is adjusted to a predetermined concentration, thereby realizing anoptimal concentration of the water-soluble cutting oil at a cuttingarea.

There is a case that the water-soluble cutting oil is different inappropriate content of water according to the types of work pieces.

As is in this case, in Example 2, on the basis of the basicconfiguration (4), the water concentration is adjusted corresponding toeach of the work pieces 1, . . . , i, . . . , n, and then the aboveadjustment makes it possible to set an appropriate content of the wateron cutting each of the work pieces 1, . . . , i, . . . , n.

INDUSTRIAL APPLICABILITY

The present invention is able to keep a cutting state without stoppingby continuously supplying cutting oil to a cutting area of a machinetool for cutting work pieces and, therefore, can be used in all types ofmachine tools for cutting work pieces.

What is claimed is:
 1. A method for supplying cutting oil in a machinetool for cutting plural kinds of work pieces, comprising the steps of:a: in advance of cutting the work pieces 1, . . . , i, . . . , n,setting cutting times t₁, . . . , t_(i), . . . , t_(n) for each workpiece 1, . . . , i, . . . , n and selecting a cutting oil to be used,wherein n is an integer of not less than two, and associating a kind ofwork with each ith work piece, b: setting quantities q₁, . . . , q_(i),. . . , q_(n) of the cutting oil supplied to the work pieces 1, . . . ,i, . . . , n per unit time in accordance with the cutting area of thework pieces 1, . . . , i, . . . , n, c: setting a quantity q′ as a fixedvalue to be supplied to the cutting-oil tank per unit time, wherein forsome i₀<n:q′≤(V+q ₁ t ₁ + . . . +q _(i0) t _(i0))/(t ₁ + . . . +t ₀) andq′≥(q ₁ t ₁ + . . . +q _(n) t _(n))/(t ₁ + . . . +t _(i0)) wherein V isthe volume of the cutting-oil tank, and the quantity of the oil in thecutting-oil tank before cutting is set to be zero, and supplying thecutting oil to the cutting-oil tank by the quantity q′ over a period oftime t₁+ . . . +t_(i0), and thereafter not supplying the cutting oil tothe cutting-oil tank, d: supplying the cutting oil, from the cutting-oiltank, to the cutting area at a rate of q₁t₁, . . . , q_(i)t_(i), . . . ,q_(n)t_(n) for cutting the work pieces 1, . . . , i, . . . , n.
 2. Themethod for supplying cutting oil according to claim 1, wherein whenwater-soluble cutting oil is adopted, adjusting a content ratio of thecutting oil to the water inside the cutting-oil tank to a predeterminedconcentration.